Rough terrain (RD cranes are arguably the most popular machine in the crane industry. RT cranes have all-wheel drive, all-wheel steer, and a single operator's cab. They are perfectly suited for the broadest range of terrain usage. Due to the crane's low speed gearing, large off highway earth mover tires, and short wheelbase, the crane is only capable of speeds up to 25 MPH. Self-propelled highway travel is not possible with the RT crane. One way of transporting the crane over the highway is to load it onto the bed of a large highway hauling trailer. This is time consuming, awkward, and expensive. Another way to transport the crane is to suspend the crane above the highway between a tractor and a dolly. When this is done, and particularly for heavier cranes, the weight of the crane and its boom exert substantial forces on the tractor and dolly connections. Moreover, when the crane reaches the job site the tractor and dolly must be completely disconnected before lifting operations can be performed.